Lamp, filament therefor and method



March 31,'1953 N. J. RAlNoNE 2,633,552

LAMP, FILAMENT THEREFOR AND METHOD Filed June 4, 1951 iff-g. INVENToRA'TTORN EY Patented Mar. 31, LA1953 LAMP, FILAMENT THEREFOR AND METHODNicholas J. Rainone, Passaic, N. J., assigner to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of Pennsylvania-Application June 4, 1951,- Serial No. 229,759

Claims. l

This invention relates to lamps and, more particularly, to filaments forprojection lamps.

The conventional filament for an incandescent electric lamp, such as aprojection lamp, isa biplane ten-section iilamentary translation devicehaving the first and last sections for mounting, the second and thirdand eighth and ninth sections as outer sections, and the remaining foursections as inner or center sections. Y

v Before the development of coil bending machines as disclosed in U. S.Patent No. 2,449,653, issued September 21, 1948, such sectional lamentswere differentially wound on a coil winding machine with three to livemm. spaces or open turns between sections. The laments were hand formedby bending this open turn between sections over a hot knife. By thismethod it was possible, through the use of the proper cam arrangement onthe coil winding machines, to wind the outer sections with a closerpitch than the center sections of the filament.

However, because of the relatively large space between sections on sucha differentially wound filament, it is not possible at present to bendthe sections on the new coil bending or forming machine. A continuouslywound coil having an overall length undesirably longer than thedifferential coil is used. The machine-forming method is extremelydesirablev in the production of filaments, as the rate is three timesthat of the hand forming method.

In projection lamp operation, the center or inner sections of thefilament are mutually heated by one another and by the adjacent outersections. Also, the outer sections are cooled to a greater extent thanthe innerV sections by conduction through and convection currents in thegas in the enclosing bulb or envelope. Hence, the center sections tendto operate at a higher temperature than the outer sections, therebygiving both non-uniform lament temperature and resultant screenillumination. In addiiton, such center sections tend to develop hotspots which shorten the life of the lamps. Further, a nonuniform lightsource is difficult to focus and ciecreases the screen intensity.

` This defect was formerly compensated for and reasonably corrected bythe differentially wound lament having a smaller Vpitch and consequentlymore turns in: the'outer sections having the same length as thecentersections ofthe fila-vr ment. However, with the newcoil forming 0rbending machines, the 'diiferentially wound sectional filament'` has notbeenusable. "Hence, it hasbeen' found advantageous, ac-

(Cl. S13-344) cording to my invention, to employ the following methodsof filament manufacture which permit use of the desirablemachine-forming method and give a more uniformly heated lamentary lightsource which will increase screen intensity and uniformity, facilitatefocusing, and give a longer lamp life:

1. The method of sectional filament manufacture comprising machinewinding a differential coil having a smaller pitch in the outer sectionsthan in the inner sections and only small breaks between sections, andmachine forming the coil into a biplane sectional lament.

2. The method of continuous filament manufacture comprising machinewinding a continuous coil having a pitch which is desired in the laterformed outer sections, machine bending the coil into a biplane iilamenthaving more turns in the outer sections than in the center sections, andstretching while hot the center sections to the same length as the outersections.

3. The method of continuous filament manufacture comprising machinewinding a continuous coil having a pitch which is desired in the laterformed center sections, machine bending the coil into a biplane filamenthaving more turns in the outer sections than the center sections, andcompressing while hot the outer sectionsto the same length as the centersections.

4. The methodof continuous filament manufacture comprising machinewinding a continuous coil at a pitch Which is desired in the laterformed outer sections, selecting from each end of the coil a sufficientnumber of turns to comprise the respective outer sections, stretchingwhile hot the middle of the coil to give the desired larger pitch in thecenter sections, and machine-forming the coil into a biplane sectionalfilament.

, In its general aspect, the present invention has the object ofproducing a biplane sectional filament as a uniformly heated lightsource for a projection ,lamp `which will increase screen intensity anduniformity, facilitate focusing, and give a longer lamp life.

Y Specifically, an object of the present invention is a method offilament manufacture which permits use of the desirable machine-formingmethod.

Another specific ,object is the method of sectional filament manufacturecomprising machine winding a differential coil having a smaller pitch inthe outer sections than in the inner sections fand only a small-breakbetween sections, and machine forming .the coil into abiplanesectionalii1ame'r1t."""'`- An additional object is the method oicontinuous lament manufacture comprising machine winding a continuouscoil having a pitch which is desired in the later formed outer sections,machine bending the coil into a biplane filament having more turns inthe outer sections than in the center sections, and stretching theinner` or center sections to thev same length as:l the outer sections.

Another object is the method of continuous lament manufacture comprisingmachine wind"-v ing a continuous coil having a pitch which. is. desiredin the later formed center sections, ma-

chine bending the coil into a biplane` izllament` having more turns inthe outer sections thanv the center sections, and compressing` underheat the outer sections to the same length as the center sections.

A further object is the method of continuous iilament manufacturecomprising machine winding a continuous coil at a. pitch which isdesired inthe later formed; outer sectionsselectinggfrom each end ofthecoit asuiiicient; number Qi turns to comprise the respective outersectionsi stretch* ing-while hot theA middle. of: the coii to'. givethe. desired larger ptchn the center sections, andmachine forming thecoil into a bi-plane fila..b ment.

Other objects. and? advantages.. ot' the invention will' appearv tothose: skilled in the; art. to which it` appertains as the.descriptionproceeds', both bydirect-recitation-andi byV implicationiromthe context. A

Referringtovthe.E accompanying drawingr 1n which likev numerals ofvreference refer to similar partsv throughout:

Fig'. l is an elevational view-- of." a projection lamp embodying myinvention.;

Fig; 2' is an elevational viewf of. a biplaneV sec;- tional filamenti-orthe projection lampY ofFig;l;

Fig. 3 is a topviewf of the iilamentofy 2;

Fig. 4" isan# eleva-tional: view: oi" a differentially wound sectionalcoil; prior to machine. bending;

Fig. 5v is an elevational view: ci.` a. portion'. of the coil-windingmachine;

Fig. 6 is an elevationallviewof a iiiament for the projectionlamp ofFig. l', after machine bending but prior tostretching;

Fig; is-anV elevational view oiacontinuously wound coilI for thefila-ment' of Fig; 6;

Fig. 8; is-an' elevational view off-a filament of theprojection-lamp-of-'Fig ll,y aftermachine bending but prior tocompressing while hot;

Fig. 9 isarr elevational viewl of a continuously Wound coil vaftervstretching the middleof said coil.

Referring to the` drawings in detail7 thereAVV is shown a projectionlamp I-I designated'iorfbasedown operation and comprising a vitreousenvelope I2 with its upper closed`- end painted black for alight shieldanda base I3', and' enclosing a mount I4.

The mount I4- comprises` a stem i51 sealed to the envelopei^2-andprovided with an exhaust tube I6 opening through-a' pressA IRleading-in and supporting conductors i8 and- I-Sl extending through thepressirom-thebase I-B; atop bridge i9, a iioatingbridgeA 219; twoiiiamentleg; inserts 2l and a filament 40.

The supportingconductcrs i8 and It;suitably five-piece leads, havetheirnormally vupper --ends bentto a, JV-shaped configuration with theelongatedbottom section oitheili' suitably parallel to the axis ofthelamp as illustrated` in Fig: 1; The upper or free ends of` conductorsljand Y I'S 4 are suitably nickel to facilitate the connection of the topbridge I9 thereto.

This bridge I9 consists of a short vitreous cane insulator 22 having twoouter support wires 23, suitably nickel, for afixing said bridge to theupper ends of conductors I8 and I9 and three to lament supports 24,suitably molybdenum. Wires 23 and supports @have their upper endsembedded`v in insulator 22 and: are insulated thereby from each other.The lower ends of supports 2@ are hooked, as illustrated in Fig. l, toprovide top support for thecoiled filament 40. The number of supports 24is determined by the number of coiled'sectionsa in. filament 40.

In the presenti embodiment, this filament 40 comprises 10 coiledsections which are connected. by interrsection uncoiled loops andstaggered so that five are disposed in one normally/*vertical planeparallel to that of the conductors I8 and I9 and iive in a normallyvertical plane. parallel thereto.` The sections. are. so spacedthat.in.planas;shown in Pig;v 3;,.they'lie at the vertices of isoscelesltriangles.

In this. showing the numerals; 4; and 42; re,- spectivelydesignate therst and: tenth'l sections oilament 40, as the.v fragmentary termnalsec.-tions; thenumerals 43, 44;,45 and. 46; respectively designate thesecond,l third, eighth'.l and: ninth. sections, that is,.rthe. outersections; and the: ninV morals. 41, 48, 49' and.- 50; respectivelyVdesignate the; fourth, fth.. sixth and seventh sections;that is., the;inner. sections.

The upper inter-section,uncoiled4 loops-of: the filament, d. are drapedover: ther hookediendsiof: tcpY lament support. wires.- 245 and; theterminal. portions 40. and 41| are respectivelyn electricallyconnectedzto; conductors 1 8: and i9? by means of theiilamentleginsertsf. 2I

The; filament leg. insertsi eachconsists; of.` an; ebliquely L-shapedlead. wire.. suitably nickel; around which has; been Wound; anappropriate coil. having the same: pitch. as; terminal sections 4-.Ifanddfofla-men-t 40:.. 'helowerrend of; eachinsert 2l is. screwed intothe respective termina-l section of. the lament` 40e.. The ytree;` or:upper end .of` eachinsertZ-.I` isf secured, as by welding. to the.upper. or free..end-o.` supporting-conductors I8. and.Y IS..

In order toV position lament 40 between con.- ductors [8a-nd. I9. andallow for expansionv and contraction, a floating bridgeN-issprovided.

The lower uncoiled portions of the connected sections. of. filament. 4D-arev secured by hooks inthe. upper end ot the lower.V lament supports 25of said bridge` 20. In this showinggthereare four lower supports 25.`This bridge. 2.9. comprises. a vitreous cane. insulator 2s. into. which.the. lower ends of' supports 25' areY embedded. and insulated from each,other,y two, floating. bridge. side. guides 2' anda. fioating bridge.bottom.,guide. 28. The side guidesZ'I', suitably thinmetallic. wireshave. their inner ends embeddedfin the. ends. of. the. in.- sulator 2ban their upper ends, looped" about Ieading-in conductors IB and I 9iwith. freedom to. slide thereon. The. bottom. guide.v 228,. similar toguides 2T, has its upper. end' embedded. suitablyin the. undersideof'insulatcr Z6V and. its, lower end projecting through the top. loop`of. spud 294 which' extends upwardly` from press il' in which its. lowerendV is embedded'. Aitor, insertion through. the loop of. spud,29, the..end. of. bottom guide 28 is bent over to prevent. disengagement.

After a suitable exhaust.' vwhichmay consistof a bake, ii'ush withinert.- gas, such. as nitrogen; and a nal fili of'agassuch asnitrogerratthe land 46b than in said center sections.

conventional pressure, the lamp is tipped off and the base I3 isapplied.

According to my invention, the filament 49 may be manufactured by firstmachine-winding a differential sectional coil 35, as shown in Fig. 4,having a smaller pitch in the terminal sections 4l and 42 and outersections 43, 44, 45, 4S than in the inner sections 4l, 48, 49 and 5i]and only a small break or one open turn, such as 0.3 to 0.5 mm., betweensections. This may be accomplished by a suitable cam arrangement (notshown) on thecoil-winding machine by feeding the filament wire 30 from areel 3|, as shown in Fig. 5, over rollers 32 and 33, and winding saidwire 30 on a filament mandrel 34.

The differential sectional coil 35 is thenv machine-formed on thebending machine by the method and filament-forming apparatus dis.-closed in U. S. Patent No. 2,449,653, issued September 21, 1948, so thatfive sections, namely terminal section 4I, outer sections 44 and 43 andcenter sections 48 and 59 are in a normally vertical plane parallel to asecond normally vertical plane in which the other five sections lie. Thesections are so spaced that in plan, as shown in Fig. 3, they lie at thevertices of isosceles triangles. While a ten section differential coilis shown as a specific, embodiment of the present invention, it will beunderstood that my method may be used in making a filament of anydesired number of sections.

An alternative method for manufacturing a filament comprises machinewinding, as shown in Fig. 5, a continuous coil 36, as shown in Fig. 7,having a pitch which is desired in the later formed four outer sections,namely 43, 44, 45, and 46. Coil 36 is machine bent into filament 40, asshown in Fig. 6, having more turns in said outer sections than in thecenter sections, namely 41, 48a, 49, and 50a. The four inner or centersections are then stretched downwardly While hot to the same length asthe outer sections, thereby forming a filament equivalent to thatdesignated 40.

A further alternative method of manufacture of a filament comprisesmachine winding a continuous coil 36h, similar to the coil shown in Fig.7, except having the pitch of the later formed four center sections,namely 41, 48, 49 and 50. Coil 3Bb is then machine bent into filament40h, as shown in Fig. 8, having more turns in the outer sections, namely43, 44, 45b The outer sections are compressed under heat to the samelength as the center sections, thereby forming a filament equivalent tothat designated 40.

A still further method of producing a 'filament comprises machinewinding a continuous coil 36 having the pitch of the later-formed outersections, namely 43, 44, 45 and 46 (not shown). From each end of thecoil 36, the required number of turns is selected to form the two outersections 43 and 44 and 45 and 46 on each end, and terminal sections 4land 42. The middle of coil 36 is then stretched while hot to give thedesired center sections pitch. Coil 38, as shown in Fig. 9, is machineformed into lament equivalent to that designated 40, as shown in Fig. 2.

While preferred embodiments of my invention have been disclosed, it willbe understood that modifications may be made Within the spirit and scopeof the appended claims. Y

I claim:

1. A filament for an incandescent electric lamp having a plurality ofcoiled sections comprising terminal sections, outer sections and centersections united by looped portions, said outer sections having the samepitch as said center sections and a different length than said centersections whereby said filament may be distorted so as to make saidcenter and outer sections corresponding in length and simultaneously thepitch of the center sections different from that of said outer sections.

2. A filament for an incandescent electric lamp having a plurality ofcoiled sections comprising terminal sections, outer sections and centersections united by looped portions, said sections so spaced that half ofthe sections are in a normally vertical plane parallel to the remainingsections in a normally vertical plane and that in plan said sections lieat the vertices of isosceles triangles, said outer sections having thesame pitch as said center sections and a different length than saidcenter sections whereby said filament may be distorted so as to makesaid center and'outer sections corresponding in length andsimultaneously the pitch of said center sections diferent from that ofsaid outer sections.

3. A filament for an incandescent electric lamp having a plurality ofcoiled sections comprising terminal sections, outer sections and centersections united by looped portions, vsaid outer sections having the samepitch as said center sections and a longer length than said centersections whereby said center sections may be stretched to correspondinglength so as to simultaneously make the pitch of the center sectionslarger than that of the outer sections.

4. A filament of an incandescent electric lamp having a plurality ofcoiled sections comprising terminal sections, outer sections and centersections united by looped portions, said outer sections having the samepitch as said center sections and a longer length than said centersections whereby said outer sections may be compressed to correspondinglength so as to simultaneously make the pitch of the outer sectionssmaller than that of the center sections.

5. A filament for an incandescent electric lamp having a plurality ofcoiled sections comprising terminal sections, outer sections and centersections joined together at their ends, said outer sections having thesame pitch as said center sections and a different length than saidcenter sections whereby said filament may be distorted so as to makesaid center and outer sections correspond in length and simultaneouslythe pitch of the center sections different from that of said outersections.

' NICHOLAS' J. RAINO'NE.

REFERENCES CITED The following references are of record in the lejofthis patent:

UNITED STATES PATENTS Number Name Date v 1,632,769 Severin June 14, 19271,726,480 Fehse Aug. 27, 1929 2,167,765 McGowan Aug. 1, 1939 2,434,478Allen Jan. 13, 1948 2,449,653 Isaac et a1. Sept. 21, 1948 2,449,679 VanHorn Sept. 21, 1948 Y

